1. Field of the Invention
The present invention relates to an imaging apparatus for picking up, recording, and displaying a still image or a moving image and to a control method of the imaging apparatus.
2. Description of the Related Art
In recent years, functions for executing an image processing to areas other than an object is installed in many imaging apparatuses such as digital camera, digital video camera, and the like. For example, as one of those functions, there is a function of artificially providing a shading effect to a background area of photographed image data, or the like. Generally, in the case of an imaging apparatus such as a single lens reflex camera in which an imaging element is of a large size, by opening an iris so as to increase a focal length, a depth of field becomes shallow and it is relatively easy to photograph an image so that the background other than the object which is in focus is blurred as mentioned above. On the other hand, in an imaging apparatus in which an imaging element is of a small size such as a compact digital camera or the like, even if the foregoing method is used, since there is a tendency that the depth of field becomes deep, it is difficult to photograph image data in which a background is blurred.
There is known such a technique that in consideration of the foregoing problem, by discriminating an object area and a background area of the photographed image data and executing a filtering processing to the background area, even in the imaging apparatus in which the imaging element is of a small size such as a compact digital camera or the like, the image data in which the background is shaded can be obtained. Japanese Patent Application Laid-Open No. 2007-124398 discloses such a technique that a spatial frequency component is obtained from the photographed image data in order to discriminate an object area and a background area. That is, according to the technique disclosed in Japanese Patent Application Laid-Open No. 2007-124398, a position of a focus lens is adjusted so that the object is located at a distant end of the depth of field, thereby increasing a blur amount on the background side in the photographed image data. A spatial frequency component amount of each of a plurality of divided blocks is calculated and the block is determined as an object area on the basis of whether or not such a value is equal to or greater than a threshold value.
However, according to the technique disclosed in Japanese Patent Application Laid-Open No. 2007-124398, since the area discrimination is performed based on the spatial frequency component amounts of the image data of one image, there is such a problem that when the blur amount on the background area side is small, an enough precision is not obtained. Particularly, in the imaging apparatus in which the imaging element is small such as a compact digital camera which is widespread in recent years, since there is such a tendency that even if the foregoing processing is executed, an enough blur amount is not obtained, it is difficult to perform the area discrimination based on the spatial frequency component amounts of the image data of one frame.